Geographically isolated antennas

ABSTRACT

Briefly, in accordance with one or more embodiments, a base transceiver station having a first set of antennas and a second set of antennas geographically separated from the first set of antennas transmits a reference signal to a first device, and receives feedback from the first device. The feedback represents information that can be used to construct a weight adjustment vector. The base transceiver station selects a precoding vector from a codebook based at least in part on the feedback received from the first device, calculates the weight adjustment vector based at least in part on the feedback, and applies the weight adjustment vector to the selected precoding vector to provide an adjusted precoding vector. The base transceiver station then may transmit data to the first device using the adjusted precoding vector.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. application Ser. No.13/966,694 filed Sep. 20, 2013, which in turn is the National StageApplication of International Application No. PCT/US2012/031692 filed onMar. 30, 2012, which in turn claims the benefit of U.S. ProvisionalApplication No. 61/542,086 filed on Sep. 30, 2011. Said application Ser.No. 13/966,694, said Application No. PCT/US2012/031692, and saidApplication No. 61/542,086 are hereby incorporated herein by referencein their entireties.

BACKGROUND

Geographically isolated antennas may be deployed to provide enhanceddownlink multiple input, multiple output (MIMO) transmissions. Forexample, such a deployment may be utilized for indoor antennadeployment, in heterogeneous networks, coordinated multipoint (CoMP)transmissions wherein join transmission may be considered as one or moregeographically separated antennas in a single cell. However,geographically isolated antennas may present potential issues such aswith reference signal received power (RSRP) measurements or resultingantenna gain imbalance (AGI) caused by the large antenna separationdistance between different antennas. Geographically separated antennasubsets may experience different channel conditions resulting in severeAGI which may potentially impact performance of the system. Currentsystems assume that all antennas of a base station or enhanced node B(eNB) in a cell are geographically co-located. The RSRP measurements areonly obtained for one or two antennas, for example from common referencesignal (CRS) port 0 or port 1, and the measurements are applied to allof the antennas of the system. However, the assumption may not be validfor geographically separated antennas that experience different channelconditions depending on their specific location, and as a result themeasurements will not adequately reflect the real conditions of thecell.

DESCRIPTION OF THE DRAWING FIGURES

Claimed subject matter is particularly pointed out and distinctlyclaimed in the concluding portion of the specification. However, suchsubject matter may be understood by reference to the following detaileddescription when read with the accompanying drawings in which:

FIG. 1 is a diagram of an enhanced Node B (eNB) having geographicallyseparated antennas in accordance with one or more embodiments;

FIG. 2 is a diagram of an enhanced Node B (eNB) having geographicallyseparated antennas in a cell utilizing a remote radio unit (RRU) inaccordance with one or more embodiments;

FIG. 3 is a diagram of an enhanced Node B (eNB) utilizing a codebook toselect a precoding vector based at least in part on a channel conditionin accordance with one or more embodiments;

FIG. 4 is a flow diagram of a method to adjust the codebook forgeographically separated antennas based at least in part on measuredantenna gain imbalance (AGI) in accordance with one or more embodiments;

FIG. 5 is a flow diagram of an alternative method to adjust the codebookfor geographically separated antennas based at least in part on measuredantenna gain imbalance (AGI) in accordance with one or more embodiments;

FIG. 6 is a flow diagram of a method to adjust the codebook forgeographically separated antennas based at least in part on channelstate indicator reference signals (CSI-RS) based RSRP measurement inaccordance with one or more embodiments;

FIG. 7 is a block diagram of an information handling system capable ofadjusting a codebook for geographically separated antennas in accordancewith one or more embodiments; and

FIG. 8 is an isometric view of the information handling system of FIG. 7that optionally may include a touch screen in accordance with one ormore embodiments.

It will be appreciated that for simplicity and/or clarity ofillustration, elements illustrated in the figures have not necessarilybeen drawn to scale. For example, the dimensions of some of the elementsmay be exaggerated relative to other elements for clarity. Further, ifconsidered appropriate, reference numerals have been repeated among thefigures to indicate corresponding and/or analogous elements.

DETAILED DESCRIPTION

In the following detailed description, numerous specific details are setforth to provide a thorough understanding of claimed subject matter.However, it will be understood by those skilled in the art that claimedsubject matter may be practiced without these specific details. In otherinstances, well-known methods, procedures, components and/or circuitshave not been described in detail.

In the following description and/or claims, the terms coupled and/orconnected, along with their derivatives, may be used. In particularembodiments, connected may be used to indicate that two or more elementsare in direct physical and/or electrical contact with each other.Coupled may mean that two or more elements are in direct physical and/orelectrical contact. However, coupled may also mean that two or moreelements may not be in direct contact with each other, but yet may stillcooperate and/or interact with each other. For example, “coupled” maymean that two or more elements do not contact each other but areindirectly joined together via another element or intermediate elements.Finally, the terms “on,” “overlying,” and “over” may be used in thefollowing description and claims. “On,” “overlying,” and “over” may beused to indicate that two or more elements are in direct physicalcontact with each other. However, “over” may also mean that two or moreelements are not in direct contact with each other. For example, “over”may mean that one element is above another element but not contact eachother and may have another element or elements in between the twoelements. Furthermore, the term “and/or” may mean “and”, it may mean“or”, it may mean “exclusive-or”, it may mean “one”, it may mean “some,but not all”, it may mean “neither”, and/or it may mean “both”, althoughthe scope of claimed subject matter is not limited in this respect. Inthe following description and/or claims, the terms “comprise” and“include,” along with their derivatives, may be used and are intended assynonyms for each other.

Referring now to FIG. 1, a diagram of an enhanced Node B (eNB) havinggeographically separated antennas in accordance with one or moreembodiments will be discussed. As shown in FIG. 1, a wireless network100 may comprise an enhanced Node B (eNB) 110 serving one or more userequipment (UE) devices such as UE 116, UE 118, UE 120, and UE 120 in theembodiment shown. The eNB 110 may have multiple antennas, for example afirst set of antennas 112 and a second set of antennas 114 wherein thefirst set of antennas 112 and the second set of antennas 114 may begeographically separated by a significant distance. In other words, thefirst set of antennas 112 and the second set of antennas 114 are notco-located. In such an arrangement, a first group of UE devices such asUE 116 and UE 118 may be in communication with the eNB 112 via the firstset of antennas 112, and a second group of UE devices such as UE 120 andUE 122 may be in communication with the eNB 110 via the second set ofantennas 114. It should be noted that the eNB 110 and the UE devices maybe operating in compliance with a Long Term Evolution (LTE) standardand/or any developments or advancements of such a standard, for exampleLTE-Advanced, wherein network 100 may comprise an LTE network. Ingeneral, eNB 110 may be referred to generically as a base transceiverstation or just a base station, and any one or more of the UEs may bereferred to generically as a mobile station, mobile device, or justdevice, and the scope of the claimed subject matter is not limited inthese respects. It should be noted network 100 may be discussed hereinas an LTE network for purposes of discussion, but network 100 maycomprise any type of wireless network such as a wireless wide areanetwork (WWAN), a wireless local area network (WLAN), or the like, incompliance with any various wireless network standard such as aWorldwide Interoperability for Microwave Access (WiMAX) network incompliance with an Institute of Electrical and Electronics Engineers(IEEE) 802.16e standard, a WiMAX-II network in compliance with an IEEE802.16m standard, and so on, and the scope of the claimed subject matteris not limited in this respect.

As shown in FIG. 1, since the two sets of antennas of eNB 110 aregeographically separated, the first set of antennas 112 may experiencedifferent channel conditions than that of the second set of antennas114. As a result, there may be resulting antenna gain imbalance (AGI)among the antennas of the eNB 110. In such a situation, any channelmeasurements made with the first set of antennas 112, for examplereference signal received power (RSRP) measurements, may not be validfor the second set of antennas 114. For example, in the current LTEspecification, the RSRP measurement utilizes common reference signal(CRS) port 0 and optionally utilizes CRS port 1, both of which may bemapped to the first set of antennas 112. The measurements for the firstset of antennas 112 are then applied to all of the antennas of eNB 110including the second set of antennas 114. However, with any AGIresulting from the geographically separated antennas, the measurementstaken on only one set of antennas cannot be applied to the other sets ofantennas. As a result, adjustments may be made in order to accommodatefor such AGI as discussed in further detail, below.

Referring now to FIG. 2, a diagram of an enhanced Node B (eNB) havinggeographically separated antennas in a cell utilizing a remote radiounit (RRU) in accordance with one or more embodiments will be discussed.In the example shown in FIG. 2, enhanced Node B (eNB) 110 of network 200may serve three cells such as Cell 0, Cell 1, and Cell 2. The first setof antennas 112 of eNB 110 may be utilized to communicate with userequipment (UE) 116 that is in close proximity to the first set ofantennas 112. UE devices that are located toward a distal region of anyof the cells away from the eNB 110, such as UE 120, may communicate witheNB 110 via a second set of antennas 114 that are geographicallyseparated in a cell from the first set of antennas 112. In someembodiments, the second set of antennas 114 may be the antennas of aremote radio unit (RRU) 210 coupled to eNB 110, for example in aCoordinated Multipoint (CoMP) deployment. In some embodiments, multipleRRUs coupled to eNB 110 may be utilized within a single cell wherein theRRUs have a corresponding additional set of antennas to communicate withone or more UEs depending on the location of the UE with respect to eNB110 and given RRU, signal strength, channel conditions, and so on. Itshould be noted, however, that FIG. 2 illustrates an example deploymentof multiple sets of geographically separated antennas using one or moreRRUs, and the scope of the claimed subject matter is not limited in thisrespect.

Referring now to FIG. 3, a diagram of an enhanced Node B (eNB) utilizinga codebook to select a precoding vector based at least in part on achannel condition in accordance with one or more embodiments will bediscussed. As shown in FIG. 3, the enhanced Node B (eNB) 110 may utilizea codebook 316 to select an appropriate precoding vector W based atleast in part on a condition of the channel H 314. In such anarrangement, the transmitter of the transceiver 310 of eNB 110 transmitsreference signals to the receiver of the transceiver 312 of userequipment (UE) 116. The UE 116 then may estimate the channel via channelestimation block 314 as determined from the received reference signals.The UE 116 may then provide feedback to the eNB 110, for example as aprecoding matrix index (PMI), that is utilized by the eNB 100 to selectan appropriate precoding vector from the codebook 316. The eNB 110 maythen transmit data to the UE 116 using the precoding vector to weightthe transmitted data to accommodate for the conditions of the channel H314. In one or more embodiments, the precoding vector W may be adjustedvia adjustment of the codebook 316 in order to accommodate any antennagain imbalance (AGI) that is detected between two or more sets ofgeographically separated antennas.

Referring now to FIG. 4, a flow diagram of a method to adjust thecodebook for geographically separated antennas based at least in part onmeasured antenna gain imbalance (AGI) in accordance with one or moreembodiments will be discussed. Although method 400 of FIG. 4 illustratesone particular embodiment of a method to adjust a codebook 316, otherembodiments of method 400 may include greater or fewer blocks thanshown, and/or in various different orders, and the scope of the claimedsubject matter is not limited in this respect. Method 400 adjusts thecodebook 316 based at least in part on a determined AGI among two ormore sets of antennas of eNB 110. Since the codebook 316 of a currentLong Term Evolution (LTE) standard is designed for co-located antennaswithout considering AGI, on one or more embodiments, the AGI may bedetermined at least in part, and an appropriate adjustment of theprecoding vector may be performed as follows:

W _(adj) =G*W _(org)

wherein W_(org) is the original precoding vector from the codebook 316,G is the weight adjustment vector, and W_(adj) is the precoding vectorafter adjustment with the weight adjustment vector. The weightadjustment vector G is able to indicate the relative value of antennagain for the distributed antennas of the multiple sets of antennas thatmay experience AGI. In one or more embodiments, the weight adjustmentvector G may be derived from reference signal received power (RSRP)measurements reported by the UE 116, or alternatively by soundingreference signals (RS) measured at the eNB 110. For example, the weightadjustment vector G may be calculated as follows:

G=diag([RSRP₁RSRP₂ . . . RSRPn_(t)])

wherein n_(t) represents the number of transmission antennas at the eNB110. Method 400 represents one embodiment to implement utilizing aweight adjustment vector G to adjust the precoding vector obtained fromcodebook 316. The approach of method 400 may be referred to asnon-transparent to the UE 116 wherein the UE 116 adjusts the codebook316 with the weight adjustment vector G before the precoding matrixindicator (PMI) search. In such an embodiment, reference signals aretransmitted from the eNB 110 to the UE 116 at block 410. The UE 116 thenestimates the channel at block 412 using the received reference signals.The UE 116 then calculates the weight adjustment vector G at block 414which may be based at least in part on the reference signals, forexample RSRP measurements. The UE 116 utilizes the weight adjustmentvector G in the PMI search at block 416 and provides PMI feedback to theeNB 110. With this PMI feedback received from the UE 116, the eNB 110selects a precoding vector from the codebook 316 at block 418 based onthe PMI feedback and applies the adjustment vector G to the selectedprecoding vector at block 420. The weight adjustment vector G iscalculated or reconstructed by the eNB 110 from RSRP feedback orsounding reference signal (RS). The eNB 110 may then transmit data atblock 422 using the adjusted precoding vector.

Referring now to FIG. 5, a flow diagram of an alternative method toadjust the codebook for geographically separated antennas based at leastin part on measured antenna gain imbalance (AGI) in accordance with oneor more embodiments will be discussed. Although method 500 of FIG. 5illustrates one particular embodiment of a method to adjust a codebook316, other embodiments of method 500 may include greater or fewer blocksthan shown, and/or in various different orders, and the scope of theclaimed subject matter is not limited in this respect. Method 500 ofFIG. 5 is similar to method 400 of FIG. 4 except that method 500 may bereferred to as transparent to the UE 116 wherein the UE 116 searches andfeeds back the precoding matrix indicator (PMI) without codebookadjustment by the UE 116. In such an embodiment, the eNB 100 transmitsreference signals to the UE 116 at block 510, and the UE 116 estimatesthe channel at block 512. The UE 116 then provides PMI feedback to theeNB 110 at block 514 without having the UE 116 provide any adjustment tothe codebook 316 or without the UE 116 calculating the weight adjustmentvector G. Based on RSRP feedback received from the UE 116 or on asounding reference signal (RS), the eNB 110 calculates the weightadjustment vector G at block 516, and at block 518 adjusts the precodingvector selected from the codebook 316 based on the PMI feedback byapplying the calculated weight adjustment vector. The weight adjustmentvector may be obtained by the eNB 110 from a sounding RS measurement orother measurement. The eNB 110 may then transmit data at block 520 usingthe thus adjusted precoding vector. In one or more embodiments, aphysical downlink shared channel (PDSCH) may be decoded based at leastin part on such RS measurements, which may obviate any need forstandardization for the UE transparent method 500, although the scope ofthe claimed subject matter is not limited in this respect.

Referring now to FIG. 6, a flow diagram of a method to adjust thecodebook for geographically separated antennas based at least in part onchannel state indicator reference signals (CSI-RS) based RSRPmeasurement in accordance with one or more embodiments will bediscussed. Although method 600 of FIG. 6 illustrates one particularembodiment of a method to adjust a codebook 316, other embodiments ofmethod 600 may include greater or fewer blocks than shown, and/or invarious different orders, and the scope of the claimed subject matter isnot limited in this respect. FIG. 6 illustrates approach to obtainreference signal received power (RSRP) measurements for the respectiveantennas of geographically separated antenna sets wherein the codebook316 may be adjusted using such RSRP measurements. In a generaldeployment, each antenna of eNB 110 may have a corresponding channelstate indicator reference signals (CSI-RS or just CRS) port. Byobtaining RSRP measurements for all of the CRS ports, the RSRPmeasurements may be utilized to determine the performance differenceamong different sets of geographically separated antennas. Thus, in oneor more embodiments the CRS ports may be mapped at block 610 to multipleantennas of eNB 110 including to the sets of geographically separatedantennas. In one or more particular embodiments, CRS ports may be mappedto fewer than all of the antennas, for example where each respective setof antennas is mapped with at least one CRS port. Then, per port RSRPmeasurements may be made at block 612 using the CSI-RS ports for themapped antennas. In such embodiments per port RSRP measurements may bemade for the mapped CSI-RS ports. The UE 116 then feeds back the RSRPmeasurements to the eNB 110 at block 614. The eNB 110 calculates theweight adjustment vector G at block 616 using the RSRP measurementswhich may be utilized at block 618 to adjust the precoding vectorobtained from the codebook 316. The eNB 110 may then transmit data to UE116 using the adjusted precoding vector 620. In one or more embodiments,the Layer 3 mobility measurements may be adjusted according to themethod 600 of FIG. 6, although the scope of the claimed subject matteris not limited in this respect.

Referring now to FIG. 7, a block diagram of an information handlingsystem capable of adjusting a codebook for geographically separatedantennas in accordance with one or more embodiments will be discussed.Information handling system 700 of FIG. 7 may tangibly embody one ormore of any of the network elements, infrastructure nodes, or devices ofthe network 100 or network 200 as shown in and described with respect toFIG. 1 or FIG. 2. For example, information handling system 700 mayrepresent the hardware of eNB 110, UE 116, and/or RRU 118, with greateror fewer components depending on the hardware specifications of theparticular device, node, or network element. Although informationhandling system 700 represents one example of several types of computingplatforms, information handling system 700 may include more or fewerelements and/or different arrangements of elements than shown in FIG. 7,and the scope of the claimed subject matter is not limited in theserespects.

In one or more embodiments, information handling system 700 may includean applications processor 710 and a baseband processor 712. Applicationsprocessor 710 may be utilized as a general purpose processor to runapplications and the various subsystems for information handling system700. Applications processor 710 may include a single core oralternatively may include multiple processing cores wherein one or moreof the cores may comprise a digital signal processor or digital signalprocessing core. Furthermore, applications processor 710 may include agraphics processor or coprocessor disposed on the same chip, oralternatively a graphics processor coupled to applications processor 710may comprise a separate, discrete graphics chip. Applications processor710 may include on board memory such as cache memory, and further may becoupled to external memory devices such as synchronous dynamic randomaccess memory (SDRAM) 714 for storing and/or executing applicationsduring operation, and NAND flash 716 for storing applications and/ordata even when information handling system 700 is powered off. Basebandprocessor 712 may control the broadband radio functions for informationhandling system 700. Baseband processor 712 may store code forcontrolling such broadband radio functions in a NOR flash 718. Basebandprocessor 712 controls a wireless wide area network (WWAN) transceiver720 which is used for modulating and/or demodulating broadband networksignals, for example for communicating via a 3GPP LTE network or thelike as discussed herein with respect to FIG. 2. The WWAN transceiver720 couples to one or more power amps 722 respectively coupled to one ormore antennas 724 for sending and receiving radio-frequency signals viathe WWAN broadband network. The baseband processor 712 also may controla wireless local area network (WLAN) transceiver 726 coupled to one ormore suitable antennas 728 and which may be capable of communicating viaa Wi-Fi, Bluetooth, and/or an amplitude modulation (AM) or frequencymodulation (FM) radio standard including an IEEE 802.11 a/b/g/n standardor the like. It should be noted that these are merely exampleimplementations for applications processor 710 and baseband processor712, and the scope of the claimed subject matter is not limited in theserespects. For example, any one or more of SDRAM 714, NAND flash 716and/or NOR flash 718 may comprise other types of memory technology suchas magnetic memory, chalcogenide memory, phase change memory, or ovonicmemory, and the scope of the claimed subject matter is not limited inthis respect.

In one or more embodiments, applications processor 710 may drive adisplay 730 for displaying various information or data, and may furtherreceive touch input from a user via a touch screen 732 for example via afinger or a stylus. An ambient light sensor 734 may be utilized todetect an amount of ambient light in which information handling system700 is operating, for example to control a brightness or contrast valuefor display 730 as a function of the intensity of ambient light detectedby ambient light sensor 734. One or more cameras 736 may be utilized tocapture images that are processed by applications processor 710 and/orat least temporarily stored in NAND flash 716. Furthermore, applicationsprocessor may couple to a gyroscope 738, accelerometer 740, magnetometer742, audio coder/decoder (CODEC) 744, and/or global positioning system(GPS) controller 746 coupled to an appropriate GPS antenna 748, fordetection of various environmental properties including location,movement, and/or orientation of information handling system 700.Alternatively, controller 746 may comprise a Global Navigation SatelliteSystem (GNSS) controller. Audio CODEC 744 may be coupled to one or moreaudio ports 750 to provide microphone input and speaker outputs eithervia internal devices and/or via external devices coupled to informationhandling system via the audio ports 750, for example via a headphone andmicrophone jack. In addition, applications processor 710 may couple toone or more input/output (I/O) transceivers 752 to couple to one or moreI/O ports 754 such as a universal serial bus (USB) port, ahigh-definition multimedia interface (HDMI) port, a serial port, and soon. Furthermore, one or more of the I/O transceivers 752 may couple toone or more memory slots 756 for optional removable memory such assecure digital (SD) card or a subscriber identity module (SIM) card,although the scope of the claimed subject matter is not limited in theserespects.

Referring now to FIG. 8, an isometric view of the information handlingsystem of FIG. 7 that optionally may include a touch screen inaccordance with one or more embodiments will be discussed. FIG. 8 showsan example implementation of information handling system 700 of FIG. 7tangibly embodied as a cellular telephone, smartphone, or tablet typedevice or the like. In one or more embodiments, the information handlingsystem 700 may comprise any one of the user equipment (UE) devices ofFIG. 1 or FIG. 2, although the scope of the claimed subject matter isnot limited in this respect. The information handling system 700 maycomprise a housing 810 having a display 730 which may include a touchscreen 732 for receiving tactile input control and commands via a finger816 of a user and/or a via stylus 818 to control one or moreapplications processors 710. The housing 810 may house one or morecomponents of information handling system 700, for example one or moreapplications processors 710, one or more of SDRAM 714, NAND flash 716,NOR flash 718, baseband processor 712, and/or WWAN transceiver 720. Theinformation handling system 700 further may optionally include aphysical actuator area 820 which may comprise a keyboard or buttons forcontrolling information handling system via one or more buttons orswitches. The information handling system 700 may also include a memoryport or slot 756 for receiving non-volatile memory such as flash memory,for example in the form of a secure digital (SD) card or a subscriberidentity module (SIM) card. Optionally, the information handling system700 may further include one or more speakers and/or microphones 824 anda connection port 754 for connecting the information handling system 700to another electronic device, dock, display, battery charger, and so on.In addition, information handling system 700 may include a headphone orspeaker jack 828 and one or more cameras 736 on one or more sides of thehousing 810. It should be noted that the information handling system 700of FIG. 8 may include more or fewer elements than shown, in variousarrangements, and the scope of the claimed subject matter is not limitedin this respect.

Although the claimed subject matter has been described with a certaindegree of particularity, it should be recognized that elements thereofmay be altered by persons skilled in the art without departing from thespirit and/or scope of claimed subject matter. It is believed that thesubject matter pertaining to geographically isolated antennas and/ormany of its attendant utilities will be understood by the forgoingdescription, and it will be apparent that various changes may be made inthe form, construction and/or arrangement of the components thereofwithout departing from the scope of the claimed subject matter orwithout sacrificing all of its material advantages, the form hereinbefore described being merely an explanatory embodiment thereof, and/orfurther without providing substantial change thereto. It is theintention of the claims to encompass and/or include such changes.

What is claimed is:
 1. A method to adjust a codebook, comprising:transmitting a reference signal to a first device from a basetransceiver station having a first set of antennas and a second set ofantennas geographically separated from the first set of antennas;receiving feedback from the first device, the feedback representinginformation that can be used to construct a weight adjustment vector;selecting a precoding vector from a codebook based at least in part onthe feedback received from the first device; calculating the weightadjustment vector based at least in part on the feedback and applyingthe weight adjustment vector to the selected precoding vector to providean adjusted precoding vector; and transmitting data to the first deviceusing the adjusted precoding vector.